1. Field of the Invention
The present invention relates to a device which automatically positions a movable member such as a work pallet to a reference member such as a table of a machine tool.
2. Explanation of Related Art
The automatic positioning device of this kind generally fits a circular positioning hole provided by opening a supported surface of a movable member onto a plug which projects from a supporting surface of a reference member (for example, see Japanese Patent Public Disclosure No. 57-27640).
The conventional technique has to provide a predetermined fitting gap between the positioning hole and the plug so as to smoothly fit the former to the latter. Therefore, the fitting gap reduces the positioning accuracy.
The present invention has an object to provide a device which can automatically perform a positioning operation with a high accuracy.
In order to accomplish the above object, the present invention has constructed an automatic positioning device in the following manner, for example, as shown in FIGS. 1A and 1B, in FIGS. 4A and 4B or in FIG. 5.
The automatic positioning device comprises a reference member 2 having a supporting surface 2a which receives a supported surface 3a of a movable member 3. The movable member 3 has the supported surface 3a opened to provide a positioning hole 5 which is formed substantially circular. A plug member 12 to be inserted into the positioning hole 5 projects from the reference member 2 in a direction to a leading end and is fixed to the reference member 2. The plug member 12 is provided with a slant outer surface 13 which approaches an axis as it goes in the direction to the leading end. The plug member 12 has an outer periphery above which an annular intermediate member 15 is arranged so that at least peripheral one part of the intermediate member 15 radially expands and contracts. The intermediate member 15 is provided with a straight outer surface 16 which is fitted into the positioning hole 5 and with a slant inner surface 17 which opposes to the slant outer surface 13 of the plug member 12. A pull member 21 is axially movably inserted into the plug member 12 and has a leading end portion connected to the intermediate member 15. A locking means 31 and a releasing means 32 are provided within the reference member 2. The locking means 31 moves the intermediate member 15 for locking in a direction to a base end through the pull member 21. On the other hand, the releasing means 32 moves the intermediate member 15 for releasing in the direction to the leading end through the pull member 21.
The present invention offers the following function and advantages.
When positioning the movable member to the reference member, first, the positioning hole of the movable member is fitted onto the plug member of the reference member and thereafter the locking means drives the intermediate member in the direction to the base end through the pull member. Then the slant inner surface of the intermediate member makes a wedging engagement with the slant outer surface of the plug member directly or indirectly, thereby expanding at least one part of the intermediate member radially outwards. This tightly attaches the straight outer surface of the intermediate member to the positioning hole. Simultaneously, the pull member pushes the movable member to the reference member through the tightly attached intermediate member.
On the other hand, when releasing the locked movable member, it is sufficient if the releasing means drives the intermediate member in the direction to the leading end through the pull member. Then the wedging engagement between the slant outer surface and the slant inner surface is cancelled to result in contracting at least one part of the intermediate member radially inwards. This can cancel the tightly attached condition between the straight outer surface of the intermediate member and the positioning hole. Thereafter, it is sufficient if the movable member is separated from the reference member.
The present invention can remove the fitting clearance after the positioning hole and the intermediate member have been fitted to each other. In consequence, it can smoothly fit these positioning hole and intermediate member to each other and at the same time perform the positioning operation with a high accuracy. Besides, since the locking means and the releasing means are provided within the reference member, it is possible to automatically perform the positioning operation and cancel the positioning operation and in addition to prevent chips, dust and the like foreign matters from invading interior areas of the locking means and the releasing means.
Further, at the time of the lock driving, the pull member pushes the movable member to the reference member through the intermediate member. Therefore, depending on the needs, an exclusive clamping means may be omitted.
The present invention includes the following device.
For example, as shown in FIGS. 1A and 1B, the intermediate member 15 comprises a thin-walled cylinder and has an annular wall 15a. The annular wall 15a has at least one part constructed so that it can elastically deform radially outwards and return radially inwards by its own elastic restoring force. The intermediate member 15 has an inner periphery provided with the slant inner surface 17 in plural number, which are spaced apart from each other peripherally at a predetermined interval. This invention can make the outer surface of the intermediate member without forming any clearance. Therefore, it can prevent chips, dust and the like foreign matters from invading a space inside the intermediate member. This makes it possible to use the positioning device for a long period of time with maintenance free.
Further, the present invention includes the following device.
For example, as shown in FIGS. 1A and 1B, the slant outer surface 13 is provided in plural number on the outer periphery of the plug member 12 as spaced apart from each other peripherally at a predetermined interval and a rolling member 18 is inserted into a space defined between every slant outer surface 13 and every slant inner surface 17. This invention can engage the slant outer surface with the slant inner surface and disengage the former from the latter smoothly through the rolling member.
Moreover, the present invention includes the following device.
For example, as shown in FIGS. 4A and 4B, at least one slit 51 which extends axially is provided in the annular wall 15a of the intermediate member 15, so that the annular wall 15a can elastically deform radically outwards and return radially inwards by its own elastic restoring force. This invention facilitates to process the intermediate member simply and precisely and besides can increase a radial elastic deformation amount of the intermediate member greatly.
The present invention, for example, as shown in FIGS. 4A and 4B, may attach rubber or the like resilient sealing member 52 to the slit 51. In this case, the resilient sealing member can prevent foreign matters from invading the space inside the intermediate member.
The present invention, for example, as shown in FIG. 1B or FIG. 4B, includes a device wherein the intermediate member 15 is formed over its substantially entire periphery with the straight outer surface 16. This invention can increase an area of the tight attachment between the intermediate member and the positioning hole, which results in the possibility of performing the positioning operation with a higher accuracy.
The present invention, for example, as shown in FIG. 6, includes a device wherein the intermediate member 15 is provided with the straight outer surface 16 in plural number as spaced apart from each other peripherally. This invention can decrease a tight attachment area of the straight outer surface to result in the possibility of securing a large press force.
Additionally, the present invention includes the following device.
For instance, as shown in FIG. 6, the intermediate member 15 is attached to the plug member 12 so that the former is inhibited from rotating around the axis. The intermediate member 15 is provided with a pair of the straight outer surfaces 16, 16 which oppose to one another. Relief surfaces, 71, 71 are formed by concaving portions defined between the paired straight surfaces 16, 16. According to this invention, the paired relief surfaces can fit the intermediate member and the positioning hole to each other smoothly, which results in making the fitting operation easy and reliable.
Moreover, the present invention includes the following device.
For instance, as shown in FIG. 5, at least one of the plug member 12, the intermediate member 15 and the pull member 21 is opened to provide a discharge port 64, 65, 66 for discharging cleaning pressurized fluid. According to this invention, since the pressurized fluid can blow off the foreign matters attached to the positioning device, the positioning operation can be performed assuredly with a high accuracy.
Furthermore, the present invention, for example, as shown in FIG. 4A, includes a device wherein the slant inner surface 17 directly engages with the slant outer surface 13. This invention can provide a positioning device which is simple and compact.